Two separate studies have been completed which indicate that environmental conditions, in these cases fluctuating temperature and humidity, can alter the host-Arbovirus relationship of snowshoe hares when compared to controls held at constant temperature-humidity conditions. Experimental group viremias were significantly higher (P less than 0.05) on days 1,2,3 than controls. Duration of viremia was 3.57 days for experimental hares compared to 2.51 days for controls. This difference was significant at P less than 0.01. Viremia onset in experimental animals was sooner than controls and was found to be significant at P less than 0.05. Almost all antibody titers for experimental hares were significantly higher than controls (P less than 0.05). In an additional study conducted in June of the same year, two groups of reproductively active hares (n equals 6) were inoculated with 3 x 10 to the 5th power SMLD50 WEE virus and exposed to the same environmental program as the February study. There was no difference in either viremia titer or time of onset between experimental and control groups; however, viremia duration, 3.2 days in experimental hares vs. 2.2 days for controls, was highly significant (P less than 0.001). Work over the coming year will be directed toward three main goals: 1) additional monitoring of the response of the hare under constant laboratory and fluctuating "field" conditions, 2) attempts to identify the underlying mechanism of augmentation of viremia and 3) development of techniques to more frequently obtain samples from the experimental animals.